Moon Jelly (Aurelia aurita)

Moon Jelly (Aurelia aurita)
Moon Jelly (Aurelia aurita)
by B. N. Sullivan

This week we commemorate the 45th anniversary of the first moon landing  (by Apollo 11 on July 20, 1969) with a photo of a Scyphozoan known as the Moon Jelly.  Jellies of the genus Aurelia are common in coastal waters worldwide, including the Arctic.

In the photo you can see the four oral arms suspended from the body of the jelly, arranged around the critter's mouth.  Along the edge of the bell of the Moon Jelly are tiny hair-like tentacles -- not really visible in this photo.  Both the tentacles and the oral arms bear nematocysts, the stinging cells used for defense and to immobilize prey.  Moon Jellies "prey" on zooplankton.

I photographed this Moon Jelly (A. aurita)  in the Aegean Sea, just a few meters from the shore near Vouliagmeni, Greece.  This one was about a foot (30 cm) in diameter, although some nearly half again as large have been recorded.

The Spiny Puffer's Message: You can't touch this!

Spiny Balloonfish (Diodon holocanthus)
Spiny Balloonfish (Diodon holocanthus)
by B. N. Sullivan

You can't touch this... and you definitely can't swallow it!

That is the message that fishes in the Spiny Puffer family attempt to transmit to potential predators.  While other creatures defend themselves from predators by fleeing, or hiding, or with camouflage, members of this family (Diodontidae) inflate themselves.  In addition, evolution has armed these guys with another feature: rigid spines all over their bodies that are erected when the fish inflates.

The Spiny Puffer's spines actually are like specialized scales. When the puffer is not inflated, most of the spines lie more or less flat against the skin, but when the skin stretches during inflation, the spines go upright.

Ain't nobody gonna swallow these babies!

Puffers are not very streamlined even when they are not inflated, so they are not fast swimmers.  Once they inflate they really are ungainly.  Their little pectoral fins will flutter, but they don't attain much in the way of forward motion.  To survive, they rely entirely on making themselves look unappealing as prey.

When a Spiny Puffer is molested or feels threatened, it opens its mouth and draws sea water into its stomach.  The stomach is capable of expanding greatly -- so greatly that the stomach and its watery contents can virtually fill the whole fish, squishing the rest of its organs up against its backbone.  Its skin is stretchy, too, which also helps it to expand like a balloon.

Both fish pictured in this post are partially inflated.   Each was pottering along in a shallow reef area when we spotted them.   In each case, Jerry shined his light on the fish so that I could approach and aim the camera for a close-up of the Puffer's cute face and interesting eyes.  But these are touchy critters, and that was enough to induce them to begin to inflate, so in each instance I snapped two frames and retreated before they freaked out.

Some divers intentionally harass or even try to grab puffers, just to see them inflate.  This is quite a mean thing to do.  Remember, inflation is a defense.  If the fish begins to inflate, that means it is alarmed.  If it puffs out to its maximum, it is really scared!  This behavior may be amusing to divers, but it really stresses the poor fish.

If you see a puffer and it begins to inflate, move away from it to let it know you are not a threat.  Don't terrorize the puffers!

Spotted porcupinefish (Diodon hystrix)
Spotted  Porcupinefish (Diodon hystrix)
Both of the Spiny Puffers on this page are Caribbean species.  I photographed them on two separate night dives in the Cayman Islands.  To give you an idea of their size, each of these individuals was approximately 12-14 inches (30-35 cm) in length.

Blue Snowflake Coral (Sarcothelia edmonsoni), a Hawaiian endemic

Blue Octocoral (Sarcothelia edmonsoni), a Hawaiian endemic
Blue Snowflake Coral (Sarcothelia edmonsoni), a Hawaiian endemic Octocoral
by B. N. Sullivan

The underwater landscape in Hawaii is not known for the presence of soft corals. There are hard, stony corals aplenty on Hawaiian reefs, but the sea plumes, colorful Nephtheid soft corals, and sea fans found on most other tropical reefs around the world are largely absent in Hawaii.

The pretty blue Octocoral pictured above is one of relatively few soft coral species that live in Hawaiian waters.  Some soft corals in Hawaii are not seen by divers because they grow at depths beyond sport diving range.  Others, like this one, are overlooked more often than not.

It is easy for a diver to swim right past a patch of Blue Snowflake coral without noticing it.  The species is what we think of as a "low-rise" coral.  The colonies form mats on the surfaces of rocks and dead coral.  From a distance, the colonies look kind of "mossy."  You have to get in close to observe the tiny flower-like polyps, but once you spot those, there is no doubt that you are looking at an Octocoral.

Blue Snowflake Coral is a Hawaiian endemic, i.e., it occurs naturally only in Hawaiian waters.  Its scientific name is Sarcothelia edmonsoni, but it was formerly classified as Anthelia edmonsoni.  (If you are searching for information about the species, you may have to look up both names).  It is a member of the Xeniidae family.

Sarcothelia edmonsoni is the primary food source for another creature endemic to Hawaii, the sea slug Marionia hawaiiensis* (formerly known as Tritonia hawaiiensis).  It makes sense -- doesn't it? -- that an endemic critter would have another endemic species as its main prey.

I photographed this example of Sarcothelia edmonsoni along the South Kona coast of Hawaii's Big Island, near the edge of Honaunau Bay.

*I don't have a photo of Marionia hawaiiensis, so click here to see the creature on Cory Pittman and Pauline Fiene's site, Sea Slugs of Hawaii.

Fine perch for a sea turtle

Green Sea Turtle (Chelonia mydas)
Green Sea Turtle perched on the coral at Pulau Sipadan, Malaysia
by B. N. Sullivan

Sea turtles have a knack for finding comfy resting places on the reef.  Earlier this year I posted a photo of a turtle who had plopped down on a bed of soft corals to take her rest.  Here we have another Green Sea Turtle, perched this time on a table coral that jutted out from a steep bank.

We spotted this turtle at the outset of our dive, and as we passed by the same spot about an hour later on our way back to the boat, she was there again -- or still! -- surveying the scene.  She looked so comfy and at ease that we reckoned this must be her regular post.  We know from having observed the behavior of individual turtles in Hawaii over periods of years that each effectively "owns" a particular spot on the reef, returning to the same rocky shelf, or cavelet, or depression in the coral day after day over a long span of time.

To us, this turtle looked a bit like a sentry posted in a watchtower.  From the outcropping, she  had an unobstructed view of the entire bank -- left, right, up to the surface, and down into the gloomy depths -- a fine perch for a turtle.